LAPLACE — Did a mistake cost two local residents their lives during a 1:50 a.m. hail of gunfire on State Street in LaPlace?

Authorities, family members and the St. John the Baptist Parish community have wondered for years why 18-year-old Sierra Gregoire and 23-year-old Travis Gregoire, cousins from LaPlace, were targeted for drive-by killing on Oct. 5, 2015.

An arrest Wednesday in Slidell could finally point everyone to some answers.

“This case is very likely a case of mistaken identity, because we can’t show a tie-in as to why anybody would want to kill the Gregoires,” St. John Sheriff Mike Tregre said Thursday afternoon during discussion on the arrest of Djuan Mackey.

Tregre said detectives believe Mackey and an undetermined second suspect or suspects pulled up in a white, four-door pickup truck and opened first during the overnight hours, critically striking Sierra, Travis and wounding then 23-year-old Damarius Carter as they had just arrived in their own vehicle and were exiting.

Travis Gregoire died that morning at a LaPlace hospital after authorities pulled his body from the passenger side. Sierra Gregoire survived a few hours longer, authorities rushing her from where she collapsed near an adjacent house and bringing her to University Medical Center in New Orleans, where she passed away that evening.

A neighbor heard the gunfire and drove Carter to the hospital, where emergency medical personnel treated him for his injuries.

Police are hoping the arrest of Mackey and the community’s acute memory of the senseless violence lead to more cooperation, answers and arrests.

“We have physical evidence that ties (Mackey) to the double murder,” Tregre said.

“We believe he was one of the shooters. Even though (Mackey) has a Gretna address, he does have ties to the community. We believe those ties may have been involved with him and are kind of sweating now. We’re going to continue putting pressure on them.”

Mackey was arrested without incident Wednesday in Slidell by the U.S. Marshals Fugitive Task Force, Tregre said, noting the suspect was brought to St. John Parish, where he was jailed for two counts of second degree murder and one count of attempted second degree murder.

His bond was set at $1.25 million.

Investigation

Mackey’s arrest is the latest news in a case that generated numerous headlines when it was first reported more than two-and-a-half years ago.

The morning after the Gregoires’ deaths, authorities discovered a white truck that was believed involved in the shooting still simmering after it was set on fire in Reserve.

Two days later members of the St. John the Baptist Parish Sheriff’s Office, U.S. Marshals Fugitive Task Force, U.S. Secret Service, U.S. Homeland Security and Kenner Police Department arrested Reserve resident Derrence Greenup without incident near the airport in Kenner.

It was announced three months later that local prosecutors would not pursue charges against Greenup because video surveillance placed him in New Orleans during the time of the shooting.

Greenup’s attorney later told the New Orleans Advocate that investigators found the “murder weapon” in the attic of Greenup’s residence, but Greenup always maintained he never touched it and others had access to it.

A familiar name reemerged locally this month when Djuan Mackey was shot and wounded himself, this time on Mothers Day in LaPlace during a mid-afternoon shooting on English Colony Drive.

Mackey and another victim were struck, but police said numerous witnesses to the shootout have failed to share any valuable information with police.

Despite Mackey’s arrest May 23 and his wounding May 13, Tregre said one had little to do with the other.

“We have been building a case on him, and the timing was right for the arrest,” Tregre said. “Hopefully, with his arrest, somebody might come forward and give us a little more to help identify the other shooter.

“Solving a case is one of the best things we can do to give a family justice, even if it’s from a long time ago. We’re never going to stop, because the DNA, lab work and forensics are getting better and better.”